The invention is directed to a piezoelectric pump, particularly for ink-jet matrix printer devices, wherein a pump channel is formed by first and second piezoceramic parts arranged parallel to and at a distance from one another and wherein each piezoceramic part is provided with electrical contacts at both sides. The piezoceramic parts are polarized such that a polarization direction lies parallel to a field strength generated by applying a voltage to the contacts. A space between the piezoceramic parts is covered with a closure means. U.S. Pat. No. 4,536,097 incorporated by reference herein discloses such a multi-channel pump which is used as a piezoelectrically operated write head for an ink-jet matrix printer device. Ink channels which can directly represent the write nozzles for the ink-jet matrix printer means are formed by piezoceramic parts arranged parallel and side-by-side, and which are covered at both sides. The piezoceramic parts are electrically contacted at both sides. In this arrangement, the piezoceramic parts which limit the ink channels directly form the drive elements, and writing fluid can be ejected drop-by-drop based on the piezoelectric deformation. The electrical contacts thus lie essentially parallel to the coverings, of which at least one is directly formed of metal and can serve as a common electrode.
In this known channel matrix, two dimensions (the transverse dimensions) of the piezoceramic parts collaborate given application of an electrical voltage in order to produce a volume change in the ink channel. The third dimension (the longitudinal dimension), however, acts opposite relative to the two other dimensions. Stated in rough terms, a net volume change of +2-1=+1 thus derives as a result.
Also occurring--at least in some of the exemplary embodiments disclosed by the aforementioned patent--is that the writing fluid is in direct electrical contact with the contactings, so that the fluid must exhibit good electrical insulating properties and high electrical puncture strengths (on an order of magnitude of =1 kV/mm). The selection of usable fluids is thus greatly limited. All water-containing writing fluids are unusable in such a system.